﻿/*
$(".pinned").pin()“钉”住某个元素
将某元素“钉”在容器内

$(".pinned").pin({
	containerSelector: ".container"
})
在小尺寸的屏幕上禁用Pin效果

$(".pinned").pin({
	minWidth: 940
})
*/
(function ($) {
    "use strict";
    $.fn.pin = function (options) {
        var scrollY = 0, elements = [], disabled = false, $window = $(window);
        options = options || {};
        var recalculateLimits = function () {
            for (var i = 0, len = elements.length; i < len; i++) {
                var $this = elements[i];

                if (options.minWidth && $window.width() <= options.minWidth) {
                    if ($this.parent().is(".pin-wrapper")) { $this.unwrap(); }
                    $this.css({ width: "", left: "", top: "", position: "" });
                    if (options.activeClass) { $this.removeClass(options.activeClass); }
                    disabled = true;
                    continue;
                } else {
                    disabled = false;
                }

                var $container = options.containerSelector ? $this.closest(options.containerSelector) : $(document.body);
                var offset = $this.offset();
                var containerOffset = $container.offset();
                var parentOffset = $this.offsetParent().offset();

                if (!$this.parent().is(".pin-wrapper")) {
                    $this.wrap("<div class='pin-wrapper'>");
                }

                var pad = $.extend({
                    top: 0,
                    bottom: 0
                }, options.padding || {});

                $this.data("pin", {
                    pad: pad,
                    from: (options.containerSelector ? containerOffset.top : offset.top) - pad.top,
                    to: containerOffset.top + $container.height() - $this.outerHeight() - pad.bottom,
                    end: containerOffset.top + $container.height(),
                    parentTop: parentOffset.top
                });

                $this.css({ width: $this.outerWidth() });
                $this.parent().css("height", $this.outerHeight());
            }
        };

        var onScroll = function () {
            if (disabled) { return; }
            var
			scrollY = $window.scrollTop();

            var elmts = [];
            for (var i = 0, len = elements.length; i < len; i++) {
                var $this = $(elements[i]),
                    data = $this.data("pin");

                if (!data) { // Removed element
                    continue;
                }
                elmts.push($this);

                var from = data.from - data.pad.bottom, addtop = options.top || 0;
                var to = data.to - data.pad.top - addtop;
                if (from + $this.outerHeight() > data.end) {
                    $this.css('position', '');
                    continue;
                }
                if (from < scrollY + addtop && to > scrollY) {
                    !($this.css("position") == "fixed") && $this.css({
                        left: $this.offset().left,
                        top: data.pad.top + addtop
                    }).css("position", "fixed");
                    if (options.activeClass) { $this.addClass(options.activeClass); }
                    if (options.infun) {
                        options.infun($this);
                    }
                } else if (scrollY >= to) {
                    $this.css({
                        left: "",
                        top: to - data.parentTop + data.pad.top + addtop
                    }).css("position", "absolute");
                    if (options.activeClass) { $this.addClass(options.activeClass); }
                    if (options.outfun) {
                        options.outfun($this);
                    }
                } else {
                    $this.css({ position: "", top: "", left: "" });
                    if (options.activeClass) { $this.removeClass(options.activeClass); }
                    if (options.outfun) {
                        options.outfun($this);
                    }
                }
            }
            elements = elmts;
        };
        var update = function () { recalculateLimits(); onScroll(); };
        this.each(function () {
            var $this = $(this),
                data = $(this).data('pin') || {};

            if (data && data.update) { return; }
            elements.push($this);
            $("img", this).one("load", recalculateLimits);
            data.update = update;
            $(this).data('pin', data);
        });
        $window.scroll(onScroll);
        $window.resize(function () { recalculateLimits(); });
        recalculateLimits();
        $window.load(update);
        return this;
    };
})(jQuery);